One-pot synthesis of self-assembled coral-like hierarchical architecture constructed by polymorphic CoSe2 nanocrystals as superior electrocatalyst for hydrogen evolution reaction

Abstract It is imperative to exploit highly efficient and stable non-precious electrocatalyst, particularly consisting of low-cost and earth-abundant elements, to produce clean hydrogen energy via hydrogen evolution reaction. To realize this target, herein, for the first time, self-assembled coral-like hierarchical network being formed from polymorphic CoSe 2 nanocrystals is synthesized by a one-pot dimethylformamide-solvothermal reaction. This non-precious transition-metal dichalcogenide exhibits superior hydrogen-evolution performance: it has an ultra-small Tafel slope of 31.6 mV dec −1 , which is comparable to that of commercial Pt/C catalyst; moreover, it delivers a quite low onset overpotential of ∼126 mV and very large cathode current density of −60 mA cm -2  at −250 mV overpotential; most importantly, it demonstrates favorable stability even after 1500 cycles. The outstanding electrocatalytic performance is attributed to its unique coral-like porous hierarchical structure established by conductive CoSe 2 nanocrystals, which can not only offer abundant electrocatalytic active sites, but also boost the ability of charge transportation. We expect that the precious metal-free electrocatalysts with high efficiency and low production cost for hydrogen evolution reaction could be prepared through our proposed rational design strategy in this work.